Arnic calendar

From Themys Project

The Arnic calendar is a secular and religious solar calendar and the most commonly used timekeeping standard in the world. Its epoch is based upon the Calamity of Arna, the year of which represents Year One. Dates in this era are usually denoted AC (After Calamity), while prior years are reckoned as BC (Before Calamity).

The Arnic calendar is divided into 12 months of 30 to 31 days each, in addition to one leap day placed at the end of the year, known as the interannum, which generally coincides with the Winter solstice. A regular Arnic year consists of 365 days, with a leap year of 366 days occurring roughly every four years. This second leap day is added in between the sixth and seventh months of the year and is likewise not part of any month or week. Its intercalation makes it a perennial calendar, meaning that there is a permanent equivalence between specific days of the month and specific weekdays.


The origins of the Arnic calendar are unknown, with proof of its usage dating as far back as the 1000s BC. This early period saw the employment of several distinct points of reference for timekeeping, such as the political terms of Consuls or the Regnal eras of Emperors, or more rarely in relation to the traditional year of the founding of Arna (1159 BC).

In the aftermath of the Calamity of Arna, the massive scale of the event and the political instability associated with it made the usage of Regnal eras dubious, with multiple claimants to the Imperial throne and the Imperial city itself completely destroyed. So it was that the Calamity Era came to be established, at first informally, and later on as the standard adopted by the Faith of the Sixteen.


A week in the Arnic calendar is a time unit equal to seven days. It is the standard time period used for cycles of rest days. The Classical or Calendar week begins on Sunday and ends on the rest day of Saturday, while the Modern or Common week begins on Monday and ends on Saturday and Sunday, which collectively form the weekend.

Classical or Calendar week
1 2 3 4 5 6 7
Sunday Monday Tuesday Wednesday Thursday Friday Saturday
Modern or Common week
1 2 3 4 5 6 7
Monday Tuesday Wednesday Thursday Friday Saturday Sunday


A month in the Arnic calendar is a time unit equal to 30 to 31 days, with each seasonal quarter made up of three months of 31, 30 and 30 days respectively.

Date format

The legal and cultural standards for writing dates vary between countries that employ the Arnic calendar, particularly in relation to endianness. The following table shows inscription standards in big-endian (YYYY/MM/DD) and small-endian (DD/MM/YYYY) formats. Dates for the Leap Day and Year-End are conventionally represented by using the first and final letters of the alphabet respectively. Below are examples in the Valentian alphabet, where the letters A and Z are used, as well as in the Arnic alphabet, where the letters Ava and Yis are used instead.

Arnic date standards
Format Scaldset 15th 1590
15th of the Harvest 1590
Year-End 1590 Leap Day 1590
YYYY/MM/DD 1590/07/15 1590/Z
DD/MM/YYYY 15/07/1590 Z/1590 A/1590